Israel's Prime Minister Benjamin Netanyahu has said the only way to peacefully stop Iran from developing nuclear weapons is to combine tough sanctions with a credible military threat.
Speaking at the UN General Assembly, Mr Netanyahu said Israel was ready to stand alone in defending itself.
"Don't let up the pressure (on Iran)," he told the assembly in New York.
Mr Netanyahu said the only deal that could be made with Iran's President Hassan Rouhani was one that "fully dismantles Iran's nuclear weapons programme".
He said: "Rouhani is a wolf in sheep's clothing. A wolf who thinks he can pull the wool over the eyes of the international community.
"But like everyone else, I wish we could believe Rouhani's words, but we must focus on Iran's action."
Iran has said its nuclear programme is for civilian purposes and Mr Rouhani told the assembly last month that it would never develop nuclear weapons.
There have been signs that relations between Iran and the West are thawing, with Mr Rouhani speaking on the telephone with US President Barack Obama last Friday.
The call was the highest level contact between the US and Iran since 1979.
Iranian Foreign Minister Mohammad Javad Zarif and US Secretary of State John Kerry also held talks in New York last week.
After meeting with Mr Netanyahu yesterday, Mr Obama reiterated his determination to prevent Iran from getting nuclear arms.
Both leaders said their countries were cooperating on the issue.
Mr Netanyahu made clear in his address that Israel, believed to have the Middle East's only atomic arsenal, was prepared to resort to unilateral military action against Iran if it deems diplomacy a dead end.